Joint for electric power cables



Jan. 29, 1946. T. R. SCOTT 2,393,935

` JOINT FOR ELECTRIC PowER CABLES Filed March 24, 1942 mented Jan. 29, 194s Y 2,393,935 :om ron ELEcmc rownn cannes Thomas Robertson Scott. London W. C.

2, England, anignor to Federal Telephone and Radio Corporation Application Marchv 24, 1942, Serial N0. 436,021

, In Great Britain October 81, 1941l 14 Claims. (Cl. 174-84) This invention relates to Joints for elastic power cables; and has for its object to provided satisfactory Joint between the ends of two dissimilar cables, namely, a paper-insulated cable and a rubber-insulated cable.

The invention consists in wrapping or taping the Joint with a tape of fibrous material which has been impregnated with a mixture of rubber and polystyrene. This material will unite with both ends oi the Iioint. v

The general method of making the joint would be like that described in my prior patents Nos. 2,272,615 and 2,298,654 relating to a coldprocess of making a styrenated paper Joint, the basting or painting material applied between the layers being diluted if necessary to prevent undue swelling of the styrene. The principal difiiculty, however, appears to lie with the first layer of tape on the rubber insulation, owing to the facts that monomeric styrene both swells rubber and dinuses through it: on its iirst application to the rubber insulation the monomeric styrene will vigorously swell the superncial layer, but eventually it/ will diiluse throughout the rubber and thus reduce the original swelling at the surface. Accordingly it is a further feature of the invention that the basting material applied to the 'insula tion of the rubber cable shall be a mixture of polystyrene and monostyreneA applied sparingly so that the content of monomeric styreneis comparatively low: the polystyrene is introduced into the swollen rubber to prevent undue reduction of the swelling while at the same time helping to bind the rubber to the styrene rubber coating of the i'abric tape.

The tape which is impregnated with rubber and polystyrene preferably consists of acetylated cotton (cotopa), Ior acetyiated paper, the acetylation being desirable because the tape then p03- sesses a low hygroscoplc value.

The drawing shows a cable Joint in accordance with this invention. .The cables i and 2 to be jointed 4are stripped oi their protective coverings', e. g., lead sheaths, textile braiding. proof tapes, etc., so that for a suiilcient distance (dependent o n the voltage rating oi the cables) from the exposed conductors (i `and 2 respectively) the insulation consists ofimpregnated paper-I and vulcanised rubber I respectively. After cpnnect ing the conductors I and l by well known connecting means lthe two insulations I and I are basted with a mixture of polystrene and :monostyrene (to which a suitable plasticiser may have been added). One or more layers of nbrous tape I impregnated with rubber/styrene (plasticised 6I if desired and/or loaded with solid insulating material by the well known process of milling, etc.) are then lapped over the joint, each layer after application being Painted or basted with the basting mixture.

'I'he paper insulated cable will have a lead sheath I. 'I'he rubber cable may or may not have a lead sheath I. If it has it will be desirable to apply by well known methods a metallic sleeve lil forming a waterproof junction between the two'lead sheaths. In such a case it may be convenient to restrict the lapping of the Joint to one ortwo layers and to illl in the space within the sleeve with compound 1 containing polystyrene. Il and l2 are the usual wiped joints. It the rubber cable has no lead sheath it will be necessary to build up the lapped insulation to a point at which the paper insulation of the one cable is suillciently shielded from moisture abmption. It may be found desirable to extend the metallic sheathing of the cable by lapping over the `ioint iiexible metallic tape, e. g., lead foil, care being taken to terminate this in such a way over the rubber cable that no concentration of electrical stress is set up. It may be con venient to terminate the protective coverings. e. g.. proofed tape and/or compounded braiding oi' the rubber cable over this metallic tape.

The processes described may be applied to either single conductor or multi-conductor cables.

What 'is claimed is:

1. A. cable joint comprising a paper-insulated cable joined tc a rubber-insulated cable, a brous tape impregnated with a mixture of rubber and polystyrene wrapped around the connected cables andthe paper and rubber insulation adjacent the connection.

2. A joint as claimed in claim 1, in which the brous tapehas a low hygroscopic value about equal tothat of acetylated cellulose.

8. A Joint as claimed in claim 1 in which the brous tape is of acetylated cotton.

4. A cable Joint according to claim 1, in combination with a thin illm of a polystyrene-mono- -styrene mixture over the rubber insulation and beneath the iibrous tape.

5. A cable joint according to claim 1, in combination with a thin illm of a polystyrene-monostyrene mixture over the paper and rubber insulations and beneath the fibrous tape.

6. A; cable joint according to claim 1, in combination with a thin nlm o! a polystyrene-monostyrene mixture intermediate the wrappings of i the iibrous tape.

7. A cable Joint according to claim 1, in combination with thin nlms ot a polystyrene-monostyrene mixture over the paper and rubber insulations and intermediate the wrapping o! the fibrous tape.

8. A cable Joint cOmPrisinz a DRW-insulated cable joined to a rubber-insulated cable, said cables beins provided with outer aheaths, the abutting conductor ends of the cables bein: bared andjoinedbyaconnectinsmeanaaiibroustape impregnated with a mixture of rubber and polystyrene the bared conductors and the paper and rubber insulation adjacent the connectiomandasleeveoverthewrawinloi tape extending between the sheaths of the cables.

9. A cable joint according to claim 8, including a polystyrene nllinz between the sleeve and the @De Wrapping.

10. A cable joint comprising a paper-insulated cable joined tos. rubber-insulated cable.r abrous tape impregnated with a mixture o! rubber. poly- Y styrene and a plasticiser, wrapped aroiuid the connectingcablesandthepaperandmbberinsulation adjacent to the connection.

i1. A method o! lforming a cable ioint between a peper-insulated cable and a rubber-insulated cable which comprises forming a Joint between the cable conductors. bastin: the end portion ot therubberinsulationwithamixtureoipolystyrene` and monostyrene sparingly applied. and wrapping a vfibrous tape impregnatedl with a mixtul' 0f 4rubber md Wbltn'cne around the cable joint and the ends of the paper and rubber insulation.

p 12. A method as outlined in claim 1l in which the nbmus tape is bashed with a mixture of polystyrene and monoetyrene. t

.13. A method as set forth in claim l1 in which the wrapping and bastin: operations are carried out in the cold. l

14. The method according te claim 11 in which the paper insulation as well as the rubber insulation is basted with a mixture of polystyrene and monostyrene. sparingly applied.

THOMAS ROBERTSON scorri'. 

